Laboratory, Field and Farm Based Assessment of Compost and Compost Teas for Vegetable Crop Health

View the project final report

Commodities

• Vegetables: tomatoes

Practices

• Crop Production: biological inoculants, foliar feeding
• Education and Training: extension, on-farm/ranch research
• Pest Management: biological control, compost extracts
• Soil Management: earthworms

Field and greenhouse studies were conducted to evaluate the potential for use of a vermicompost-based aerated compost tea to control septoria leaf spot disease in tomato. In each of four trials conducted during 2003 and 2004, plants treated with weekly sprays of compost tea were healthier than plants sprayed with water, and as healthy as those treated with mancozeb at recommended rates. In the trial conducted at Wichita. Kansas, during the summer of 2003, yield of number 1 tomatoes was significantly higher from compost tea treated plants than from other treatments. Vermicompost-based compost tea may prove useful to organic tomato growers.

Introduction:

Compost tea (CT) is getting increased attention and is being used as an alternative plant disease control measure in organic horticulture (NOSB, 2004). An increasing body of experimental evidence indicates that plant disease can be suppressed by treating plant surfaces with a variety of water-based compost preparations (Scheuerell and Mahaffee, 2002). CT differs from compost extracts, compost leachates, or manure teas in the methods of production (Diver, 2002).

CTs are aqueous extracts of compost that are prepared using various processes, which may include specialized brewers and added ingredients that may also culture the organisms being extracted from the compost, including bacteria, fungi, protozoa and nematodes (Ingham, 2002). CTs may be produced by methods that include active aerating during the brewing process (ACT) or with more passive methods that do not include active aeration after initial mixing (NCT). Both ACT and NCT methods rely on specific recipes, well-characterized (high quality) compost, and aqueous extraction for defined periods of time.
CT applied to foliage has been demonstrated to suppress a range of foliar diseases (Scheuerell and Mahaffee, 2002); however most of the studies reported on CT to date, have used NCT (Hoitink, 1990) and much of the research on microbial communities involved in compost-induced suppressiveness of plant diseases has focused on compost or compost-amended soil; and not on aerated compost tea (Scheuerell and Mahaffee, 2002).

Inconsistent results have been a hallmark of efforts to use aerated compost tea for disease suppression. Many factors likely contribute to this inconsistency, including compost quality, added nutrients, brewing time, temperature, and water quality, sufficient levels of aeration during brewing, specific disease being controlled, and local environmental condition.

Diseases are a limiting factor in tomato production in many parts of the world and can be particularly challenging for organic growers. Septoria leaf spot caused by the fungus Septoria lycopersici and early blight caused by Alternaria solani are often severe in Kansas (Marr et al, 1995). These diseases may occur anytime during the growing season, but septoria leaf spot generally becomes more severe after fruit-set, affecting older foliage, while early blight can attack leaves, stems and fruits. Recommended control practices for these diseases include use of wilt resistant varieties, a 3 to 4 year rotation with unrelated crops, and fungicide sprays (Egel et al., 2004). Organic producers have fewer options for disease control on tomatoes and other vegetables and may suffer significant yield losses.

The objective of this study was to evaluate the potential of ACT made from vermicompost to suppress septoria leaf spot and early blight of tomato in Kansas. Experiments were conducted in the field and greenhouse to compare the disease suppressiveness of CTs with fungicide-treated and untreated controls. Experiments also included application of CT to root and leaf surfaces, and the use of various recipes in order to test hypotheses related to modes of compost tea action and to evaluate parameters related to compost tea quality.

A short-term outcome of this project will be enhanced knowledge by cooperating farmers and researchers about compost and compost tea quality, related to disease suppression on vegetable crops, particularly tomato. Intermediate outcomes may include expanded use of compost tea by organic and conventional growers for improved vegetable crop health. Intermediate outcomes may also include a continuation of researcher/grower cooperation to design and implement studies on the use of compost tea to improve vegetable crop health. Longer term outcomes of a successful compost tea research project will include widespread adoption of appropriate use of compost and compost tea, leading to improvements of yields and quality of vegetable and other crops, and to reductions in the use of synthetic pesticides by conventional growers. If successful this project will contribute directly to the overall desired outcomes of SARE, including a) improving the profitability of producers and associated businesses and b) sustaining and improving the environmental quality and natural resources base on which agriculture depends (through reduction in pesticide use and enhancement of soil biological activity).